Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
NDA2022General AbilityGeneral ScienceActual

Two convex lenses have focal lengths of 50 cm and 25 cm ,respectively. If these two lenses are placed in contact, then the net power of this combination will be equal to

Options

  1. A+2 dioptre
  2. B+6 dioptre
  3. C-6 dioptre
  4. D+3 dioptre

Correct answer

B. +6 dioptre

Step-by-step solution

The focal length ( F ) of the combined convex lens is given by formula, 1 / F =1 / fl +1 / f 2 (where f 1 and f 2 are the foal lengths of individual lens) Then the combined focal length will be Combined focal length ( F ):= fl 1 f 2 /[ f 1+ f 2]=50 25 /(50+25)=1250 / 75=50 / 3 ~cm =1 / 6 metre The power of the lens is calculated in Diopters (d) if the focal length is given in meters and written as P =1 / F therefore the power of the combined lens will be +6 D

Practice General Science on Quantrex Academy →

More from General Science

For an object in gravitational field, the gravitational potential is the same at two points A and B , but the gravitational field is not the same at these two points. Which one of 2026A very large container consists of an ideal gas. The speed of sound in the gas is x . When the pressure of the gas is doubled while keeping the temperature constant, the speed of s 2026A constant power machine pulls a block on a smooth horizontal surface. Which one of the following correctly describes the relation between speed of the block (v) and time (t) ? 2026A ball is dropped from rest from height h above the ground in frame S (the Earth's frame). Another frame S' is moving upwards with constant speed u relative to the Earth. In frame 2026A pendulum of length L oscillates with an angular amplitude of = 60^ and time period T . Let T₀ = 2 L g be the time period for small angle of oscillations, where g is the accelerat 2026A solid of mass m has temperature-dependent specific heat as C(T) = C₀ + T , where C₀ and are constants. The solid is heated from T₁ to T₂ . Which one of the following is the corre 2026In a certain process, the relation between pressure (P) and volume (V) , for an ideal gas, is given by PV^2 = constant . If the initial temperature is T₁ and the final temperature 2026An object is placed far beyond the centre of curvature of a concave mirror. The object then starts accelerating towards the mirror. Which one of the following is correct? 2026 Full General Science list All NDA PYQs